The present invention relates to a method and apparatus for aligning crankshaft sections and, more particularly, to a method and apparatus for the high-precision phasing of crankshaft sections during the manufacture or reassembling of pressed-together multi-cylinder engine crankshafts. Specifically, the invention relates to a novel technique and tool for aligning the center sections of pressed-together crankshafts used in personal motorized watercraft and snowmobile engines.
Crankshafts for precision machines must be accurately manufactured, or reassembled, to properly drive the engine components of the machines of which they are part. Methods and tools used in the manufacture of crankshafts are described in U.S. Pat. Nos. 4,979,335, 5,625,945 and 5,984,599. A most important aspect of such accurate manufacturing or reassembling is the alignment of the crankshaft sections. A crankshaft section usually comprises two xe2x80x9cjournalsxe2x80x9d, connected by a center pin, and one or more associated bearings. A xe2x80x9cjournalxe2x80x9d is an annular disc, or xe2x80x9cwebxe2x80x9d, with a peripheral pin transversely attached to it. Proper alignment of the crankshaft sections is particularly critical when the crankshaft sections are center sections of xe2x80x9cpressed-together crankshaftsxe2x80x9d, that is, crankshafts where the connecting center pins of at least some of the sections are press fit to one or both of the journals to which they are connected. Press fitting is the assembling of any two machined pieces by creating a bond between them as a result of the fact that one of them has been inserted within the other, so as to be properly in place, by the use of force. For example, a round connecting center pin may be press fit to a journal by providing, in the journal, an orifice with a diameter between 0.0002 and 0.004 inches smaller than the diameter of the pin, and forcing the pin into the orifice by mechanical exertion. Pressed-together crankshafts are built and reassembled by manufacturers and rebuilders such as Kawasaki, Polaris, Yamaha and others for combustion engines with several cylinders and, in particular, for combustion engines for personal motorized watercrafts, snowmobiles and similar vehicles. In contrast to pressed-together crankshafts, xe2x80x9csingle-piece crankshaftsxe2x80x9d are designed so that the journals and connecting center pins of their sections form one solid single piece, and the crankshafts themselves are usually forged in one piece. As a result, the crankshaft sections of single-piece crankshafts normally remain aligned so long as the main shaft is not accidentally bent. The crankshaft sections of pressed-together crankshafts, on the other hand, exhibit a tendency to fall out of phase during operation and as a result of normal tear and wear due to extended use. When this happens, the engines do not operate properly, or simply stop running, and they have to be taken apart so that the crankshaft sections may be properly aligned. Also, crankshafts often have to be taken apart to replace defective bearings and perform repairs or maintenance. When taken apart, the crankshaft sections usually fall out of phase and have to be re-aligned. Since crankshaft sections usually include two journals, the alignment of crankshaft sections is sometimes also referred to as the xe2x80x9calignment of crankshaft journalsxe2x80x9d. Conventional crankshaft alignment techniques can be cumbersome and time-consuming, and add substantial costs to the building and reassembling of crankshafts, particularly when the crankshafts are pressed-together crankshafts. It is apparent that a need exists, then, to provide a technique and a tool for properly and quickly aligning crankshaft sections, and, in particular, for properly and quickly aligning crankshaft sections of pressed-together crankshafts in minimum time and with minimum expense.
An object of this invention is to provide a technique and a tool for accurately aligning crankshaft sections. An object of the instant invention is also to provide a method and an apparatus for accurately and rapidly aligning pressed-together crankshaft sections, which method and apparatus may be used on practically all kinds of pressed-together crankshafts regardless of their make or origin. Another object of the invention is to provide an inexpensive method and apparatus for properly aligning the crankshaft sections normally found in the multiple-cylinder combustion engines used in personal motorized watercrafts and snowmobiles. A further object of this invention is to provide a method and a tool for the accurate, rapid and inexpensive alignment of said crankshaft sections that can be used and operated by essentially one operator with minimum amount of training. These and other objects of the invention will become apparent from the disclosure that follows.
The above objects are achieved by the phasing station tool and method of the instant invention. When used properly and in accordance with the method disclosed herein, the phasing station of this invention allows one single operator to accurately align and assemble pressed-together crankshaft sections and provide the desired degree of orientation in minimum time and with minimum expense.
The phasing station of this invention comprises a housing (also referred to as a xe2x80x9cdie shoexe2x80x9d), a phasing fixture (also referred to as a xe2x80x9cphasing jigxe2x80x9d), and crankshaft spacing means (also referred to as a xe2x80x9cspacing toolxe2x80x9d). The housing (die shoe) comprises two rigid plates, mounted in parallel fashion with respect to each other, preferably one above the other, and a plurality of linear bearing sets, mounted in perpendicular fashion with respect to the two rigid plates and in parallel fashion with respect to each other. The two rigid plates are preferably made of steel, and, for convenience, are referred to in this description as the xe2x80x9cupper platexe2x80x9d and the xe2x80x9clower platexe2x80x9d. The linear bearing sets are preferably sets of hollow tubular members, concentrically mounted with respect to each other. The inner tubular members of the linear bearing sets are attached to the lower plate; the outer tubular members of the, linear bearing sets are attached to the upper plate and have a slightly larger diameter than the inner tubular members. Preferably, the upper plate has several perforations (holes) on its surface, spaced out and of such shapes and sizes as to allow for a press fit of the outer tubular members of the linear bearing sets; and, preferably, the lower plate has several perforations (holes) on its surface, spaced out and of such shapes and sizes as to allow for a press fit of the inner tubular members of the linear bearing sets. The upper plate of the die shoe is also provided with means for attaching a hydraulic actuator assembly to its surface so as to allow a hydraulic actuator to apply pressure to and move the upper plate towards to and away from the lower plate of the die shoe. The upper, plate also has at least two, preferably threaded, perforations for bolting or otherwise securing the upper portion of the phasing jig to the plate. The lower plate has multiple perforations for receiving the alignment dowel pins of the machined steel cylinder of the lower portion of the phasing jig and locking it into different positions, as described below.
The phasing fixture (phasing jig) consists of two substantially identical metal portions so attached or placed within the phasing station as to face each other in virtual image formation: one from the upper plate of the die shoe and the other one from the lower plate. Each such substantially identical metal portion comprises a machined steel cylinder, a phasing tool and a phasing tool lock down. In addition, the lower portion of the phasing jig also comprises a centering tool and a centering tool lock down. The following is a description of the lower portion of the phasing jig, which is attachable to the lower plate. It should be understood that, except for the fact that it does not have alignment dowel pins, an orifice for mounting a centering tool, a centering tool or a centering tool lock down, the concentrically mounted upper portion of the phasing jig is identical to the lower portion, attachable to the upper plate of the die shoe and, if desired, may also be made adjustable with respect to rotation.
The machined steel cylinder of the lower portion of the phasing jig is a block of machined steel provided with several alignment dowel pins and designed to house the centering tool and the phasing tool, and receive the phasing tool lock down bolt and the centering tool lock down bolt. The machined steel cylinder is provided with an orifice for mounting the centering tool. The orifice, which is preferably circular, is concentrically positioned along the central vertical axis of the cylinder and open at both ends of said vertical axis. The machined steel cylinder of the lower portion of the phasing jig also has a second orifice, which is preferably rectangular, flanking said vertical axis and also open at both ends of the axis, for housing the phasing tool. Threaded holes are also provided along the horizontal axis of the machined steel cylinder for receiving the phasing tool lock down bolt and the centering tool lock down bolt. Means are provided for securing the machined steel cylinder to the lower plate of the die shoe.
The centering tool consists of one or more flanged metal chambers, preferably cylindrical, housing a steel centering pin, a centering spring and a tension adjustment screw. The steel centering pin has a pointed end and slides in and out along the length of the flanged metal chambers. The centering spring applies tension to the centering pin at the end opposite the pointed end of the pin. The tension adjustment screw is threaded to screw in and out of one end of the flanged metal chambers so as to allow the operator to change and control the tension on the centering pin. The flanged metal chambers have a flange at one end that allows the chambers to be securely lodged inside the machined steel cylinder orifice for mounting the centering tool. The end of the flanged metal chambers opposite the flanged end is threaded on the inside so as to allow the tension adjustment screw to move in and out and increase or decrease tension as needed.
The centering tool lock down comprises means for pressing against the centering tool, so as to keep it in place, and an orifice through one of the sides of the phasing jig adapted to accept said means. Preferably, a threaded metal bolt long enough to penetrate the orifice along the horizontal axis of the machined steel cylinder until it contacts the centering tool is used.
The phasing tool consists of one or more metal blocks with a precisely positioned and sized circular orifice along the entire length of their vertical axes. The location and the diameter of the phasing tool circular orifice are unique to the crankshaft being built or reassembled. Specifically, the distance between the center location of the longitudinal axis of the phasing tool circular orifice and the center location of the longitudinal axis of the machined steel cylinder of the phasing jig should be one-half of the stroke of the crankshaft being assembled. One-half of the stroke of the crankshaft being assembled means one-half of the distance between the farthest point and the closest point reached by the connecting rods of said crankshaft as they move about its axis. In addition, the diameter of the phasing tool circular orifice should be sized as to provide a slip fit with the mating peripheral pin of the journal of the section being aligned, as described below.
The phasing tool lock down comprises means for pressing against the phasing tool, so as to keep it in place, and an orifice through one of the sides of the phasing jig adapted to accept said means. Preferably, the orifice is threaded and adapted to receive and keep in place a threaded metal bolt in perpendicular orientation with respect to the position of the phasing tool.
The crankshaft spacing means (spacing tool) consist of suitable means for preventing the force of the hydraulic-actuator-driven upper plate of the die shoe from compressing the crankshaft section too much and failing to achieve the proper crankshaft section dimensions. Preferably, the spacing tool is made of metal and includes two identical wedge-shaped primary halves and two rectangular-shaped plates, or height-adjusting members. The four pieces. constitute a loose assembly that can be screwed together or otherwise assembled by means of strategically positioned screws and/or pins. When screwed or bolted together, the four pieces form a rectangular assembly whose height is the same as the width of the center section of the crankshaft being built or reassembled. The width of the center section of the crankshaft being built or reassembled means the distance between the two webs of said center section. The height-adjusting members of the spacing tool act as a base for the two identical wedge-shaped primary halves and, for convenience, can be made unique to the crankshaft that is being assembled. Specifically, the height of the two rectangular-shaped plates can be made to vary, depending on the crankshaft being assembled, to provide the necessary height to the four-piece assembly while allowing the operator to use the same two wedge-shaped primary halves in all alignment operations. Therefore, each spacing tool may have one or more sets of height-adjusting members.
In aligning a crankshaft section, two phasing tools are chosen in accordance with the diameters of the two peripheral pins of the journals of the crankshaft section and the stroke of the crankshaft being assembled. The two phasing tools are placed into the orifices for housing the phasing tool of the machined steel cylinder of the upper portion of the phasing jig and the machined steel cylinder of the lower portion of the phasing jig, respectively. The centering tool is inserted into the orifice for mounting the centering tool of the machined steel cylinder of the lower portion of the phasing jig. The components of the spacing tool are then selected, according to the specific requirements of the crankshaft being assembled, and the spacing tool installed between the two webs of the crankshaft section being aligned. The machined steel cylinder of the lower portion of the phasing jig is rotated with respect to the machined steel cylinder of the upper portion of the phasing jig to set the precise angular distance between the two peripheral pins of the crankshaft section at the desired radial orientation, e.g., 180xc2x0 for twin-cylinder-engine crankshafts, 120xc2x0 for three-cylinder-engine crankshafts, etc. The alignment dowel pins are next inserted into the perforations in the base of the lower portion of the phasing jig to lock the angular distance between the two peripheral pins at the set orientation. The crankshaft section is then placed in the phasing station by inserting the two peripheral pins of the journals inside the circular orifices of the two phasing tools and lining up the center longitudinal axis of the connecting center pin of the crankshaft section with the tip of the steel centering pin inside the centering tool. At this point, the desired alignment orientation has been achieved. After adjusting the tension on the steel centering pin with the tension adjustment screw to provide a flushed surface between the two journals and the flange of the centering tool, the two webs are pressed together by causing the upper plate of the die shoe to compress the center section so as to permanently lock the journals in place and preserve the desired alignment.